CA1076272A - Beneficiation of iron ores by froth flotation - Google Patents
Beneficiation of iron ores by froth flotationInfo
- Publication number
- CA1076272A CA1076272A CA284,450A CA284450A CA1076272A CA 1076272 A CA1076272 A CA 1076272A CA 284450 A CA284450 A CA 284450A CA 1076272 A CA1076272 A CA 1076272A
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- CA
- Canada
- Prior art keywords
- pulp
- ore
- iron
- conditioning
- flotation
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03D—FLOTATION; DIFFERENTIAL SEDIMENTATION
- B03D1/00—Flotation
- B03D1/001—Flotation agents
- B03D1/004—Organic compounds
- B03D1/008—Organic compounds containing oxygen
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03D—FLOTATION; DIFFERENTIAL SEDIMENTATION
- B03D1/00—Flotation
- B03D1/001—Flotation agents
- B03D1/002—Inorganic compounds
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03D—FLOTATION; DIFFERENTIAL SEDIMENTATION
- B03D2201/00—Specified effects produced by the flotation agents
- B03D2201/02—Collectors
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03D—FLOTATION; DIFFERENTIAL SEDIMENTATION
- B03D2203/00—Specified materials treated by the flotation agents; specified applications
- B03D2203/02—Ores
- B03D2203/04—Non-sulfide ores
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- Chemical & Material Sciences (AREA)
- Inorganic Chemistry (AREA)
- Paper (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
BENEFICIATION OF IRON ORES
BY FROTH FLOTATION
ABSTRACT OF THE DISCLOSURE
Iron oxides of finely-ground, low grade, siliceous oxidized iron ores can be effectively floated from the silica-bearing gangue in the presence of slime by conditioning an aqueous pulp of the ore with a reagent formed by incorporat-ing a water-soluble polyvalent metal salt into an aqueous solution of an alkali metal silicate prior to subjecting the pulp to froth flotation in the presence of an anionic type collector.
BY FROTH FLOTATION
ABSTRACT OF THE DISCLOSURE
Iron oxides of finely-ground, low grade, siliceous oxidized iron ores can be effectively floated from the silica-bearing gangue in the presence of slime by conditioning an aqueous pulp of the ore with a reagent formed by incorporat-ing a water-soluble polyvalent metal salt into an aqueous solution of an alkali metal silicate prior to subjecting the pulp to froth flotation in the presence of an anionic type collector.
Description
:1~7~7~
BI~CKGROUND 0~ Tlll' INVl~NTIO~I
This invention relatcs to the beneficiation of iron ore and, more par~icularly, to a process of bene ficiating lo~-grade, siliceous oxidized iron ores by froth flotation.
Many low-grade iron ores are too low in iron and too high in silica-bearing gangue to be suitable for use in iron and steel making processes. Consequently, such ores must be treated to separate the iron oxide content from the gangue. Froth flotation processes have been employed for this purpose. In such processes the iron oxide is floated from the silica by use of anionic collectors,or a reverse flotation scheme is employed whereby silica is floated from the iron oxide by use of cationic collectors or anionic collectors activated by a calcium ion.
Many iron ores must be ground to a very fine size to permit liberation of iron oxides from the gangue, resulting in the reduction of some of the silica and other materials ~o slimes which interfere with the flotation process. This problem can be minimized by desliming the iron ore pulp be~ore flotation. However, such a desliming step adds to processing costs and loss o the iron values.
For example, losses up to as much as 25 to 30 % of the iron are quite common in ~lotation processes including a deslim-ing step.
While eliminating grinding of the ore to a degree at whieh slimes are artificially produced would alleviate problems associated with the presence of slime, such an approach cannot be used for many ores in which the iron oxide is tightly in~rlocked wi~h silica and/or .. , .
BI~CKGROUND 0~ Tlll' INVl~NTIO~I
This invention relatcs to the beneficiation of iron ore and, more par~icularly, to a process of bene ficiating lo~-grade, siliceous oxidized iron ores by froth flotation.
Many low-grade iron ores are too low in iron and too high in silica-bearing gangue to be suitable for use in iron and steel making processes. Consequently, such ores must be treated to separate the iron oxide content from the gangue. Froth flotation processes have been employed for this purpose. In such processes the iron oxide is floated from the silica by use of anionic collectors,or a reverse flotation scheme is employed whereby silica is floated from the iron oxide by use of cationic collectors or anionic collectors activated by a calcium ion.
Many iron ores must be ground to a very fine size to permit liberation of iron oxides from the gangue, resulting in the reduction of some of the silica and other materials ~o slimes which interfere with the flotation process. This problem can be minimized by desliming the iron ore pulp be~ore flotation. However, such a desliming step adds to processing costs and loss o the iron values.
For example, losses up to as much as 25 to 30 % of the iron are quite common in ~lotation processes including a deslim-ing step.
While eliminating grinding of the ore to a degree at whieh slimes are artificially produced would alleviate problems associated with the presence of slime, such an approach cannot be used for many ores in which the iron oxide is tightly in~rlocked wi~h silica and/or .. , .
-2- ~
~7 ~ Z
other p,angue materials and fine grinding is required to obtain an acceptable liberation of the iron oxide.
Processes have been proposed wherein flotation is effected in the presence of slime; however, none have been com-mercially adopted to any appreciable extent because the concentrate is of poor quality, the process is effective for a limited number of ores, precise control of the operating condi~i.ons is required and/or the number of process steps involved, the type and quantity of reagents used, etc., result in excessive operating costs.
Examples of prior art flotation processes employing anionic type collectors for floating iron oxide from a silica-bearing gangue are disclosed in U.S. Patents 2,769,541 (Perry), 2,861,687 (Lord) and
~7 ~ Z
other p,angue materials and fine grinding is required to obtain an acceptable liberation of the iron oxide.
Processes have been proposed wherein flotation is effected in the presence of slime; however, none have been com-mercially adopted to any appreciable extent because the concentrate is of poor quality, the process is effective for a limited number of ores, precise control of the operating condi~i.ons is required and/or the number of process steps involved, the type and quantity of reagents used, etc., result in excessive operating costs.
Examples of prior art flotation processes employing anionic type collectors for floating iron oxide from a silica-bearing gangue are disclosed in U.S. Patents 2,769,541 (Perry), 2,861,687 (Lord) and
3,589,622 (Weston). Examples of prior art flotation processes in which the sillca~bearing gangue is floated from iron oxide are disclosed in U.S. Pa~ents 2,423,022 (Herkenhoff) and 3,292,780 (Frommer et al).
SUMMARY OF THE INVEMTION
The principal ob,ject of the invention is to provide a simple, efficient and economical process for bene~iciating low-grade iron ores.
Another principal object of the invention is to provide a froth flotation process which is capable of ~eparating iron oxide from siliceous iron ores without desliming and yet obtain a high recovery of the iron values.
Other aspects, advantages and objects of the invention will become apparent to those skilled in the art upon reviewing the following detailed description, ~76Z~7Z
the drawing and the appended claims.
The invention relates to a method of beneficiating siliceous oxidiæed iron ores by froth flotation oE iron oxide from silica-containing gangue including the steps of forming an aqueous pulp of the ore having a particle size suitable for froth flotation; conditioning the pulp by adding thereto a pre-mixed conditioning reagent formed by mixing a water-soluble polyvalent metal salt with an aqueous solution of an alkali metal silicate, in an amount sufficient to provide from about 0.05 to about 4 pounds of alkali metal silicate per ton of o~e, calculated as SiO2 equivalent, and to provide from about 0.02 to about 2 pounds of polyvalent metal salt per ton of ore, and by adding them to an effective amount of an anlonic collector selective to flotation of iron oxide;
and subjecting the conditioned pulp to a flotation operation whereby a concentrate containing a major portion `
of the iron oxide and a tailing relatively rich in ~
silica are produced. ;
U.S. Patent 3,337,048 (Mercade) discloses a flotation process employing an anionic collector and a dispe.rsant reagent containing sodium silicate and a poly-valent metal salt for floating colored titaniferous impurities from kaolin clay. However, it is well recogniæed that the flotation art is highly émpirical and that wide variety of factors may have a substantial or even a critical e;Efect on the degree of separation attained.
Therefore, determination of a combination of treatment reagents and/or operating conditions to obtain an effective separation of a particular mat~rial is largely unpredictable L _
SUMMARY OF THE INVEMTION
The principal ob,ject of the invention is to provide a simple, efficient and economical process for bene~iciating low-grade iron ores.
Another principal object of the invention is to provide a froth flotation process which is capable of ~eparating iron oxide from siliceous iron ores without desliming and yet obtain a high recovery of the iron values.
Other aspects, advantages and objects of the invention will become apparent to those skilled in the art upon reviewing the following detailed description, ~76Z~7Z
the drawing and the appended claims.
The invention relates to a method of beneficiating siliceous oxidiæed iron ores by froth flotation oE iron oxide from silica-containing gangue including the steps of forming an aqueous pulp of the ore having a particle size suitable for froth flotation; conditioning the pulp by adding thereto a pre-mixed conditioning reagent formed by mixing a water-soluble polyvalent metal salt with an aqueous solution of an alkali metal silicate, in an amount sufficient to provide from about 0.05 to about 4 pounds of alkali metal silicate per ton of o~e, calculated as SiO2 equivalent, and to provide from about 0.02 to about 2 pounds of polyvalent metal salt per ton of ore, and by adding them to an effective amount of an anlonic collector selective to flotation of iron oxide;
and subjecting the conditioned pulp to a flotation operation whereby a concentrate containing a major portion `
of the iron oxide and a tailing relatively rich in ~
silica are produced. ;
U.S. Patent 3,337,048 (Mercade) discloses a flotation process employing an anionic collector and a dispe.rsant reagent containing sodium silicate and a poly-valent metal salt for floating colored titaniferous impurities from kaolin clay. However, it is well recogniæed that the flotation art is highly émpirical and that wide variety of factors may have a substantial or even a critical e;Efect on the degree of separation attained.
Therefore, determination of a combination of treatment reagents and/or operating conditions to obtain an effective separation of a particular mat~rial is largely unpredictable L _
- 4 ~ ~ ~
~ ' :
bc/j~
376~Z
and can be obtained only by extensive testing and experimentation. The use of a conditioning reagent containing a water-soluble alkali metal silicate and a water-soluble polyvalent salt in combination with an anionic collector, in accordance with the invention, has been found to be surprisingly effective in the flotation of iron oxide from sllica in the presence of slimes~
, - 4a -b~ / !, ~ ~7 6~ ~
While not completcly undcrstood at this time, and the invention is not limited to any specific theory, it appears that the conditioning reagent of the invention either modifies the surface characteristics of the slime ~ particles or i~ is absorbed on the surface of the slime particles so as to prevent anionic collectors from bonding thereto and yet permits the slime particles to become wetted so they will not float during froth floation.
It appears that the conditioning reagent also modifies lQ the surface characteristics of the iron oxide particles so they can more readily ~-sorb anoinic collectors and thereby become more readily attached to air bubbles during froth flotation.
The process o~ the invention, while eliminating the cost of a desliming step, has been found to be capable of recovering up to 15 % or more iron from low-grade iron ores than present commercial flotation processes.
BRIEF DESCRIPTIOI~ OF THE DRA~JI~IG
The single drawing is a schematic flow diagram illustrating a continuous froth flotation process embodying the invention.
DESCRIPTION OF THE PREFERRED EMBODIME~TS
As is the usual case for low-grade siliceous oxidized iron ores, the ore to be treated is first ~round to a fine size feed to permit liberation of iron oxide from the silica-bearing gangue. Various conventional grinding techniques can be employed. In the specific continuous process illustrated in the flow diagram crushed ore at a nom-inal size of about 1/2 inch is introduced into a rod mill 10 along with a suficient amount of water to produce a sl.urry ., .
--5~
7 6Z~ ~ ) containin~, for example, abou~ 60 % solids.
The pulp dischar~,ed from the rod mill 10 is sub-jected to closed-circuit grinding, first being transferred to a ball mill 12 for further grinding and then to a conventional particle size classification device, such as a cyclone classi-fier 14. The ore is ground in the ball mill lZ to a pre-determined fineness desired for the subsequent froth flotation.
As is well known in the art, ~he particular partiele size to which the ore is ground depends primarily on the specific ore being processed with finer par~icle size being required for ores having the gangue more tightly interlocked with the iron oxide. Ore particles larger than the predetermined maximum size , e . g ., the underflow from the cyc1one classifi.er 14, are recirculated to the ball mill for further grinding.
The ground pulp containing particles are less than the pre-determined maximum size, e.g., the overflow from the cyclone classifier 14, is transferred to a plurality of conditioners 16a, 16b and 16c wherein the conditioning reagent, a pH
adjustment reagent and an anionic collector, respectively, is added to and mixed with the pulp prior to froth flotation.
To ob~ain the best results with most ores, the pH of the ore pulp should be within the range o about 7 to about ll, preferably within the range of about 8 to about 9, prior to conditioning. In some cases, the pH of the ore pulp may fall within the desired range without the addition of any reagents, depending on the amount and type of specific ore being treated, the state of division of the ore, the amo~mt and hardness of the water used, etc. By using a pH within these ranges, there is less ~endency ~or certain of the gangue minerals to flocculate and become entrained in the concentrate during froth flotation or, conversely, for the mineral values to be lost in the tailings.
.
~7 ~ Z
Mos~ frequently, an upward acljus~ment of the pH
o~ the pulp is required to fall within the desired range, in which case a water-soluble alkaline inorganic compound is thvroug,hly mixed with the pulp. Various water-soluble alkaline inorganic compounds conventionally used for pH
regulation are acceptable, particularly the carbon~tes and hydroxides. Soda ash presen~ly is the preferred alkaline inorganic compound; however, other compounds, such as sodium hydroxide, sodium silicate, sodium fluosilieate, sodium fluoborate, sodium phosphate, sodium borate, ammonium car-bonate and the like, may be substituted in whole or in part for the soda ash. The amount of the alkaline inorganic com-pound used depends on, among other things, the variables mentioned above and the optimum quantity is best determined empirically. Generally, the amount used for most ores will be within the range of about 0.1 to about 5 pounds per ton of ore. As used herein, the term l'ton" means short ton or 2,000 pounds avoirdupois.
The alkaline inorganic compound preferably is added to the pulp at a point in the system prior ~o the addition to the conditioning reagent. In the specific con-tinuous process iLlustrated in the 10w diagram, the alkaline inorganic compound is added to the pulp, either prior to or along with~ its introduction into the ball mill 12 for the final grinding as shown by the solid line in the flow diagram.
Optionally, the alkaline inorganic compound can be introduced into the rod mill 10 along with the water as shown by the .
dotted line in the flow diagram. ~en added at either of these points in the system, the alkaline inor~anic compound is simultaneously mixed with the pulp during grinding.
:- _7_ ~ 7 62~ 2 In cases where ~he pll o~ the pulp has to be a~just~d do~m~ardly to ~all within the desired range, an acid r~agent, such as sulfuric acid, which does not intro-duce undesirable ions into the pulp can be used for this purpose.
~ The solids content~ of the pulp during conditioning is not ~articularly critical. It can be 50 v,O or even higher depending on the particular ore or advantageously can be as low as 5 %. ~en the pulp is to be dilut~d, the additional watPr can be added to the pulp either before or after i~s introduction into the conditioner.
The conditioning reagent is added to the pulp as an aqueous solution and is ~ormed by incorporating a water-soluble polyvalent metal salt into an aqueous solution of a water-soluble alkali metal silicate. As used herein, the term "water-soluble polyvalent metal salt" encompasses metal salts containing a polyvalent metallic cation of Group Ib or higher in the ~eriodic Table, H~andboolc of Chemistry and Physics, 56th Ed., CR~ Press, Inc., (1~75) and various water-soluble hydrated salts containing such cations.
Representative examples of suitabLe polyvalent metallic cations for the polyvalent metal s~lt include irnn (ferrous and ferric), copper (cupric), aluminum, lead, chromium, manganese, cobalt, nickel, æinc, cadmium, ~agnesium, calcium, barium and mixtures thereof. Polyvalen~ metal salts containing iron (ferrous and ferric) as the cation are preferred, with those having ferric ion as the cation being the most pre-ferred, because of their availability and they contain ions common to the lattice constituents of minerals to be separated, e.g., iron oxide. It is presently believed that the iron oxide is activated by this common ion effect.
The water-soluble polyvalent metal salt can ~ ~ 7 ~ ~Z
contain various anions including ni~r~tes, sulf~tes, chlori~es and acetates.
Representative examples of water-soluble poly-valent ~etal salts which are particularly suitable for use in the conditioning reagent include ferric nitrate, ferric chloride, ferrous nitrate, ferrous sulfate, cupric sulfate, cupric nitrate, aluminum sulfa~e, aluminum nitrate, aluminum chloride, lead nitrate9 lead acetate, manganous sulfate, manganous chloride, zinc sulfate, zinc chloride and mixtures thereof.
The amount o polyvalent metal salts used is within the range of about ~ ~2 to about 2, preferably ~lithin the range o~ about 0.05 to about 1, pounds per ton of ore.
Suitable water soluble alkali metal silicates include sodium silicate, potassium silicate, and mixtures thereof with sodium silicate being preferred Particularly suitable are sodium silicates containing a weight ratio of ~a20 to SiO2 within the range of about 1:1 to about 1:3.75, preferably about 1:3.22.
The amount of alkali metal silicate used is within the range of about 0.05 to about 4, preEerably within the range of about 0.1 to about 1, pounds per ton of ore in terms of the calculated SiO2 equivalent. A
commercially available solution of sodium silicate, con-taining about 9.15 weight % Na2O, 29.5 weight % SiO2 and about 62 weight % water and marketed by Philadelphia ~uartz Co. as "O" Brand sodium silicate solution, is parti-cularly suitable for use in preparing the condi~ioning reagent. The amount of this solution used is within the range of about 0.1 to about 14, preferably within the range of about 0.3 to about 4 pounds per ton of ore.
: -9-~6~2 The conditioning, reag~nt is pr~pared by formin~, a dilu~e aqueous solution of the water-soluble polyvalent me~al salt and slowly adding this salt solution to an aqueous solution of the alkali metal silicate. In a preferred method for preparing the condi~ioning reagent, suficient water is added to the above-mentioned commercially available "O" Brand sodium silicate solutiGn to form a 5 weight ~/O
aqueous solution thereof, forming a dilute aqueous solution of the water-soluble polyvalent metal salt, e.g., a 2 weight % aqueous solu~ion of ferric nitrate, Fe~NO3)3- 9 H2O, and slowly adding the salt solution to the dilu~ed sodium , sllicate solution with stirring.
The polyvalent metal salt reacts with the sodium silicate and forms reaction products which are colloidally dispersed in the aqueous medium, Generally, the salt solution is added until the system becomes turbid without significant precipitation of the reaction products. Unless continuously agitated, the resultan~ colloidal dispersion becomes unstable within a relatively short time, e.g., within abcut 5 minutes.
If the colloidal dispersion is added to the pulp within this time period and the pulp is at a pH at the lower end o~
the above-mentioned range, it can be used as a condition-ing reagent without further trea~ment. However, such an operation ordinarily is not practical for commercial processes because it usually is more convenient to make up relatively large batches of the conditioning reagent for use as needed. Therefore, it is preferred to add a suf~i~ient amvunt of an acid reagent, such as sulfuric acid, to ~he colloidal dispersion so as to solubilize the reaction products and form a system which is stable for r 1~76Z7'~
extendcd time periods, preferably for periods up to several months. When the conditioning reagent is so stabilized, the desired amount of the active ingredients thereof can be accurately fed into the system as required.
When used, ~he amount o~ acid reagent added to the colloidal dispersion depends pri~arily upon the amount and particular type of polyvalent me~al salt used.
Generally, the acid reagen~ is slowly added to the eolloidal dispersion until it changes from a turbid condition to a clear solution and the pH of the resultant solution is within the range of about 2 to about 5 depending upon the type of mPtal salt used~ On ~he basis of the pulP, th~ amount of acid reagent used is 0 ~o about ~, preferably about 0.05 to about 1, pounds per ton of ore. The preferred ~5 weight ratio of the alkali metal silicate, in terms of the calculated SiO2 equivalent, to the polyvalent metal salt and to the acid reagent is 2:1:1.
After the conditioning reagent has been added to the pulp, it is agitated in the conditioner 16a or a suf-~0 ficient time to insure uniform dispersion thereof throughout the pulp. Generally, an agitation time of abou~ 1 to about
~ ' :
bc/j~
376~Z
and can be obtained only by extensive testing and experimentation. The use of a conditioning reagent containing a water-soluble alkali metal silicate and a water-soluble polyvalent salt in combination with an anionic collector, in accordance with the invention, has been found to be surprisingly effective in the flotation of iron oxide from sllica in the presence of slimes~
, - 4a -b~ / !, ~ ~7 6~ ~
While not completcly undcrstood at this time, and the invention is not limited to any specific theory, it appears that the conditioning reagent of the invention either modifies the surface characteristics of the slime ~ particles or i~ is absorbed on the surface of the slime particles so as to prevent anionic collectors from bonding thereto and yet permits the slime particles to become wetted so they will not float during froth floation.
It appears that the conditioning reagent also modifies lQ the surface characteristics of the iron oxide particles so they can more readily ~-sorb anoinic collectors and thereby become more readily attached to air bubbles during froth flotation.
The process o~ the invention, while eliminating the cost of a desliming step, has been found to be capable of recovering up to 15 % or more iron from low-grade iron ores than present commercial flotation processes.
BRIEF DESCRIPTIOI~ OF THE DRA~JI~IG
The single drawing is a schematic flow diagram illustrating a continuous froth flotation process embodying the invention.
DESCRIPTION OF THE PREFERRED EMBODIME~TS
As is the usual case for low-grade siliceous oxidized iron ores, the ore to be treated is first ~round to a fine size feed to permit liberation of iron oxide from the silica-bearing gangue. Various conventional grinding techniques can be employed. In the specific continuous process illustrated in the flow diagram crushed ore at a nom-inal size of about 1/2 inch is introduced into a rod mill 10 along with a suficient amount of water to produce a sl.urry ., .
--5~
7 6Z~ ~ ) containin~, for example, abou~ 60 % solids.
The pulp dischar~,ed from the rod mill 10 is sub-jected to closed-circuit grinding, first being transferred to a ball mill 12 for further grinding and then to a conventional particle size classification device, such as a cyclone classi-fier 14. The ore is ground in the ball mill lZ to a pre-determined fineness desired for the subsequent froth flotation.
As is well known in the art, ~he particular partiele size to which the ore is ground depends primarily on the specific ore being processed with finer par~icle size being required for ores having the gangue more tightly interlocked with the iron oxide. Ore particles larger than the predetermined maximum size , e . g ., the underflow from the cyc1one classifi.er 14, are recirculated to the ball mill for further grinding.
The ground pulp containing particles are less than the pre-determined maximum size, e.g., the overflow from the cyclone classifier 14, is transferred to a plurality of conditioners 16a, 16b and 16c wherein the conditioning reagent, a pH
adjustment reagent and an anionic collector, respectively, is added to and mixed with the pulp prior to froth flotation.
To ob~ain the best results with most ores, the pH of the ore pulp should be within the range o about 7 to about ll, preferably within the range of about 8 to about 9, prior to conditioning. In some cases, the pH of the ore pulp may fall within the desired range without the addition of any reagents, depending on the amount and type of specific ore being treated, the state of division of the ore, the amo~mt and hardness of the water used, etc. By using a pH within these ranges, there is less ~endency ~or certain of the gangue minerals to flocculate and become entrained in the concentrate during froth flotation or, conversely, for the mineral values to be lost in the tailings.
.
~7 ~ Z
Mos~ frequently, an upward acljus~ment of the pH
o~ the pulp is required to fall within the desired range, in which case a water-soluble alkaline inorganic compound is thvroug,hly mixed with the pulp. Various water-soluble alkaline inorganic compounds conventionally used for pH
regulation are acceptable, particularly the carbon~tes and hydroxides. Soda ash presen~ly is the preferred alkaline inorganic compound; however, other compounds, such as sodium hydroxide, sodium silicate, sodium fluosilieate, sodium fluoborate, sodium phosphate, sodium borate, ammonium car-bonate and the like, may be substituted in whole or in part for the soda ash. The amount of the alkaline inorganic com-pound used depends on, among other things, the variables mentioned above and the optimum quantity is best determined empirically. Generally, the amount used for most ores will be within the range of about 0.1 to about 5 pounds per ton of ore. As used herein, the term l'ton" means short ton or 2,000 pounds avoirdupois.
The alkaline inorganic compound preferably is added to the pulp at a point in the system prior ~o the addition to the conditioning reagent. In the specific con-tinuous process iLlustrated in the 10w diagram, the alkaline inorganic compound is added to the pulp, either prior to or along with~ its introduction into the ball mill 12 for the final grinding as shown by the solid line in the flow diagram.
Optionally, the alkaline inorganic compound can be introduced into the rod mill 10 along with the water as shown by the .
dotted line in the flow diagram. ~en added at either of these points in the system, the alkaline inor~anic compound is simultaneously mixed with the pulp during grinding.
:- _7_ ~ 7 62~ 2 In cases where ~he pll o~ the pulp has to be a~just~d do~m~ardly to ~all within the desired range, an acid r~agent, such as sulfuric acid, which does not intro-duce undesirable ions into the pulp can be used for this purpose.
~ The solids content~ of the pulp during conditioning is not ~articularly critical. It can be 50 v,O or even higher depending on the particular ore or advantageously can be as low as 5 %. ~en the pulp is to be dilut~d, the additional watPr can be added to the pulp either before or after i~s introduction into the conditioner.
The conditioning reagent is added to the pulp as an aqueous solution and is ~ormed by incorporating a water-soluble polyvalent metal salt into an aqueous solution of a water-soluble alkali metal silicate. As used herein, the term "water-soluble polyvalent metal salt" encompasses metal salts containing a polyvalent metallic cation of Group Ib or higher in the ~eriodic Table, H~andboolc of Chemistry and Physics, 56th Ed., CR~ Press, Inc., (1~75) and various water-soluble hydrated salts containing such cations.
Representative examples of suitabLe polyvalent metallic cations for the polyvalent metal s~lt include irnn (ferrous and ferric), copper (cupric), aluminum, lead, chromium, manganese, cobalt, nickel, æinc, cadmium, ~agnesium, calcium, barium and mixtures thereof. Polyvalen~ metal salts containing iron (ferrous and ferric) as the cation are preferred, with those having ferric ion as the cation being the most pre-ferred, because of their availability and they contain ions common to the lattice constituents of minerals to be separated, e.g., iron oxide. It is presently believed that the iron oxide is activated by this common ion effect.
The water-soluble polyvalent metal salt can ~ ~ 7 ~ ~Z
contain various anions including ni~r~tes, sulf~tes, chlori~es and acetates.
Representative examples of water-soluble poly-valent ~etal salts which are particularly suitable for use in the conditioning reagent include ferric nitrate, ferric chloride, ferrous nitrate, ferrous sulfate, cupric sulfate, cupric nitrate, aluminum sulfa~e, aluminum nitrate, aluminum chloride, lead nitrate9 lead acetate, manganous sulfate, manganous chloride, zinc sulfate, zinc chloride and mixtures thereof.
The amount o polyvalent metal salts used is within the range of about ~ ~2 to about 2, preferably ~lithin the range o~ about 0.05 to about 1, pounds per ton of ore.
Suitable water soluble alkali metal silicates include sodium silicate, potassium silicate, and mixtures thereof with sodium silicate being preferred Particularly suitable are sodium silicates containing a weight ratio of ~a20 to SiO2 within the range of about 1:1 to about 1:3.75, preferably about 1:3.22.
The amount of alkali metal silicate used is within the range of about 0.05 to about 4, preEerably within the range of about 0.1 to about 1, pounds per ton of ore in terms of the calculated SiO2 equivalent. A
commercially available solution of sodium silicate, con-taining about 9.15 weight % Na2O, 29.5 weight % SiO2 and about 62 weight % water and marketed by Philadelphia ~uartz Co. as "O" Brand sodium silicate solution, is parti-cularly suitable for use in preparing the condi~ioning reagent. The amount of this solution used is within the range of about 0.1 to about 14, preferably within the range of about 0.3 to about 4 pounds per ton of ore.
: -9-~6~2 The conditioning, reag~nt is pr~pared by formin~, a dilu~e aqueous solution of the water-soluble polyvalent me~al salt and slowly adding this salt solution to an aqueous solution of the alkali metal silicate. In a preferred method for preparing the condi~ioning reagent, suficient water is added to the above-mentioned commercially available "O" Brand sodium silicate solutiGn to form a 5 weight ~/O
aqueous solution thereof, forming a dilute aqueous solution of the water-soluble polyvalent metal salt, e.g., a 2 weight % aqueous solu~ion of ferric nitrate, Fe~NO3)3- 9 H2O, and slowly adding the salt solution to the dilu~ed sodium , sllicate solution with stirring.
The polyvalent metal salt reacts with the sodium silicate and forms reaction products which are colloidally dispersed in the aqueous medium, Generally, the salt solution is added until the system becomes turbid without significant precipitation of the reaction products. Unless continuously agitated, the resultan~ colloidal dispersion becomes unstable within a relatively short time, e.g., within abcut 5 minutes.
If the colloidal dispersion is added to the pulp within this time period and the pulp is at a pH at the lower end o~
the above-mentioned range, it can be used as a condition-ing reagent without further trea~ment. However, such an operation ordinarily is not practical for commercial processes because it usually is more convenient to make up relatively large batches of the conditioning reagent for use as needed. Therefore, it is preferred to add a suf~i~ient amvunt of an acid reagent, such as sulfuric acid, to ~he colloidal dispersion so as to solubilize the reaction products and form a system which is stable for r 1~76Z7'~
extendcd time periods, preferably for periods up to several months. When the conditioning reagent is so stabilized, the desired amount of the active ingredients thereof can be accurately fed into the system as required.
When used, ~he amount o~ acid reagent added to the colloidal dispersion depends pri~arily upon the amount and particular type of polyvalent me~al salt used.
Generally, the acid reagen~ is slowly added to the eolloidal dispersion until it changes from a turbid condition to a clear solution and the pH of the resultant solution is within the range of about 2 to about 5 depending upon the type of mPtal salt used~ On ~he basis of the pulP, th~ amount of acid reagent used is 0 ~o about ~, preferably about 0.05 to about 1, pounds per ton of ore. The preferred ~5 weight ratio of the alkali metal silicate, in terms of the calculated SiO2 equivalent, to the polyvalent metal salt and to the acid reagent is 2:1:1.
After the conditioning reagent has been added to the pulp, it is agitated in the conditioner 16a or a suf-~0 ficient time to insure uniform dispersion thereof throughout the pulp. Generally, an agitation time of abou~ 1 to about
5 minutes wlll be suficient for this purpose.
Following initial conditioning in the conditioner 16a, the pH of the pulp preferably is finally adjusted to a value within the range of about 6 to about 10, most preferably wlthin the range of about 8 to about 9. In some cases, the addition of the conditioning reagent may alone be sufficient to adjust the pH to the desired value, depending primarily on the amount and type of ore being processed, the amount and hardness of the water being used and whether or not the conditioning reagent contains an acid reagent. In other cases, it may be .:` . . ,, F
~7 6Z ~ ~ ' neccssarv to make a final adjustmcnt of the pll, either upw.lr~ly or downwardly, in order to obtain an optimum value when re~uired, such a final pl~ adjustmen~ most preferably is made just prior to the addition o the collector in which case the pulp is trans-ferred to the conditioner 16b. Since ~his adjustment may not be required from some ores, the condi~ioner 16b is shown in dashed lines in the flow diagram.
I~hen a downward adjustment of the pH is required, any acid reagent which does not introduce undesirable ions into the pulp is added to and thoroughly mixed with the pulp in the conditioner 16b. Generally, sulfuric acid is preferred because of its low cost and availability. In those cases where an alkaline agent is required to adjust the pH upwardly, similar conditions apply. Generally, any of the above-described water-soluble, alkaline inorganic compounds can be used ~or this purpose.
Following initial conditioning of the pulp in ~he conditioner 16a, and preferably after final pH adjustment in the conditioner 16b (when required), the pulp is transferred to conditioner 16c wherein an anionic type of collector is added to and thoroughly mixed therewith. While less desirable, the agent required for making the final adjustment of the pH of the pulp can be added to the pulp after th~ collector so long as the pulp is subsequently agitated.
Various conventional anionic collectors known to be selective or flotation of iron oxide can be used.
Suitable anionic collectors are the higher and intermediate, saturated and unsaturated fatty acids and water-soluble soaps thereof containing at least about 8 and up to about 20, preferably between 10 and 18, carbon atoms in their primary chains.
~L~7~ Z
Representativ~ ~xamples o~ suitab~e anionic collectors include ol~ic acid, linoleic acid, linolenic acid, stearic acid, palmitic acid, rosin acid, ~ish oil fatty acid, water-soluble soaps derived ~rom these acids, and mixtures of such acids and/or soaps. Fatty acids of low rosin content generally are the preferred collectors because of their lower cost and availability. Examples of particularly suîtable commercially available anionic collectors include j! PAMAK-4, which is a refined fa~ty acid collector comprised ~, .
primarily of oleic and linoleic acids and marketed by Hercules, and FA-2 and L-4 which are similar products marketed by Arizona Chemical and West Virginia Chemical, respectively.
Generally, the amount of collector used is within the range of about 0.1 to about 3, preferably within the range of about 0.5 to about 2 pounds per ton of ore.
Af~er the collector has been added, the pulp is agitated in the conditioner 16c for a sufficient time to insure uniform dispersion of the collector throughout the pulp. Generally, an agitation time of about 5 to about 20 minutes will be sufficient for this purpose.
As alluded to above, one of the advantages of the ~nvention is that the solids content of the pulp during conditioning can be substantially lower than for conventional flota~ion processes employing fatty acid collectors. Such conventional processes typically require a solids content of 50 % or more during conditioning and, consequently, intense agitation of the pulp usually is required. Also, the pulp usually must be concentrated after classification, either in a separate thickening step or concurrently with a desliming step. In either case, iron values are lost in the overflow or tailings.
7~Ei27~
In accord~nce with one aspect of the invention, conditioning can be carried out at a solids content within the range of about 5 to about 30 ~/O~ thereby eliminating the necessity for concentratin~ the pulp after cl~ssification and decreasing the energy required for agitation. On the other hand, the solids contents can be at a higher level, e.g., 50 % or higher, typically used in conventional processes.
Following final conditioning in the conditioner 16c, the conditioned pulp is processed in a conventional flotation circuit which typically includes a rough~r flotation stage 18 wherein the iron oxide floats and is separated as a concentrate in the froth and silica and other gan~ue materials report in the tailings. The froth and tailing from the rougher flota-tion stage 18 may then be subiected to a plurality of conven-tional cleaning and/or scavenging steps to improve the grade of the iron concentrate and to maxi~ize recovery of iron oxides.
Fatty acid, anionic collectors normally provide adequate frothing during re~float cleaning steps. In ~ome cases it may be necessary to add a small amount of :Euel oil or a conventional frothing agent, such as the higher alcohols (e.g., methyl isobutyl carbinol), pine oil, cresylic acid, and the like. The amount of frothing agent used depends primarily upon the number of cleaning steps involved, with lar~er amounts being used as the number of cleanin~ steps i8 increased. ~hen used, the ~rothing agent can be incorp-orated into the pulp before, after, or together with the collector and, generally, in a~ounts up to about 0.5 pounds per ton of ore. If the frothing agent is added separately, the pulp is agitated for a sufficient time to insure uniform dispersion of the frothing agënt throughout the pulp.
~ 2~ ~
Generally, an a~,itation time of up to 2 minutes will be sufficient for this purpose.
While t~e solids content of the pulp for flota-tion can vary over a wide range, i~ preferably is within the range of abou~ 5 to about 35 %. Depending on the solids content of the pulp during conditioning, it may be necessary to dilute the pulp with water to obtain the desired value for flotation.
While various conventional cleaning circuits can be used after rougher flotation, in the specific process illustrated in the flow diagram, six re flotation cleaners 20 and a scavenger 22 are used. The tailings 24 and 26 from the first and second cleaners are combined with the rougher tailing 28 and the combined tailings are passedto the scavenger 22 to produce a final tailing 32 which is transferred to a waste pond and a froth 34 which is recycled to ~he rougher 18.
The tailings 35, 36, 38 and 40 from the third, fourth, fifth and sixth cleaners are recycled to the first, second, third and fourth cleaners, respectively.
The process is generally effective for beneficiat-ing siliceous oxidized iron ore; particularly those for which conventional magnetic separation is no~ e~fective. For example, the process can be used ~or beneficia~ing iron ores o~ the type containing hematite, martite, limonite, goethite and mixtures thereof, usually referred to as oxidized ores.
The process also can be used ~or beneficiating magnetic ores, such as magnetite; however, flotation processes usually are not used for magnetic ores because magne~ic separations pro-cesses usually are less expensive. The process generally can be operated at atmospheric pressures and tempèratures, thereby -~ wlS-
Following initial conditioning in the conditioner 16a, the pH of the pulp preferably is finally adjusted to a value within the range of about 6 to about 10, most preferably wlthin the range of about 8 to about 9. In some cases, the addition of the conditioning reagent may alone be sufficient to adjust the pH to the desired value, depending primarily on the amount and type of ore being processed, the amount and hardness of the water being used and whether or not the conditioning reagent contains an acid reagent. In other cases, it may be .:` . . ,, F
~7 6Z ~ ~ ' neccssarv to make a final adjustmcnt of the pll, either upw.lr~ly or downwardly, in order to obtain an optimum value when re~uired, such a final pl~ adjustmen~ most preferably is made just prior to the addition o the collector in which case the pulp is trans-ferred to the conditioner 16b. Since ~his adjustment may not be required from some ores, the condi~ioner 16b is shown in dashed lines in the flow diagram.
I~hen a downward adjustment of the pH is required, any acid reagent which does not introduce undesirable ions into the pulp is added to and thoroughly mixed with the pulp in the conditioner 16b. Generally, sulfuric acid is preferred because of its low cost and availability. In those cases where an alkaline agent is required to adjust the pH upwardly, similar conditions apply. Generally, any of the above-described water-soluble, alkaline inorganic compounds can be used ~or this purpose.
Following initial conditioning of the pulp in ~he conditioner 16a, and preferably after final pH adjustment in the conditioner 16b (when required), the pulp is transferred to conditioner 16c wherein an anionic type of collector is added to and thoroughly mixed therewith. While less desirable, the agent required for making the final adjustment of the pH of the pulp can be added to the pulp after th~ collector so long as the pulp is subsequently agitated.
Various conventional anionic collectors known to be selective or flotation of iron oxide can be used.
Suitable anionic collectors are the higher and intermediate, saturated and unsaturated fatty acids and water-soluble soaps thereof containing at least about 8 and up to about 20, preferably between 10 and 18, carbon atoms in their primary chains.
~L~7~ Z
Representativ~ ~xamples o~ suitab~e anionic collectors include ol~ic acid, linoleic acid, linolenic acid, stearic acid, palmitic acid, rosin acid, ~ish oil fatty acid, water-soluble soaps derived ~rom these acids, and mixtures of such acids and/or soaps. Fatty acids of low rosin content generally are the preferred collectors because of their lower cost and availability. Examples of particularly suîtable commercially available anionic collectors include j! PAMAK-4, which is a refined fa~ty acid collector comprised ~, .
primarily of oleic and linoleic acids and marketed by Hercules, and FA-2 and L-4 which are similar products marketed by Arizona Chemical and West Virginia Chemical, respectively.
Generally, the amount of collector used is within the range of about 0.1 to about 3, preferably within the range of about 0.5 to about 2 pounds per ton of ore.
Af~er the collector has been added, the pulp is agitated in the conditioner 16c for a sufficient time to insure uniform dispersion of the collector throughout the pulp. Generally, an agitation time of about 5 to about 20 minutes will be sufficient for this purpose.
As alluded to above, one of the advantages of the ~nvention is that the solids content of the pulp during conditioning can be substantially lower than for conventional flota~ion processes employing fatty acid collectors. Such conventional processes typically require a solids content of 50 % or more during conditioning and, consequently, intense agitation of the pulp usually is required. Also, the pulp usually must be concentrated after classification, either in a separate thickening step or concurrently with a desliming step. In either case, iron values are lost in the overflow or tailings.
7~Ei27~
In accord~nce with one aspect of the invention, conditioning can be carried out at a solids content within the range of about 5 to about 30 ~/O~ thereby eliminating the necessity for concentratin~ the pulp after cl~ssification and decreasing the energy required for agitation. On the other hand, the solids contents can be at a higher level, e.g., 50 % or higher, typically used in conventional processes.
Following final conditioning in the conditioner 16c, the conditioned pulp is processed in a conventional flotation circuit which typically includes a rough~r flotation stage 18 wherein the iron oxide floats and is separated as a concentrate in the froth and silica and other gan~ue materials report in the tailings. The froth and tailing from the rougher flota-tion stage 18 may then be subiected to a plurality of conven-tional cleaning and/or scavenging steps to improve the grade of the iron concentrate and to maxi~ize recovery of iron oxides.
Fatty acid, anionic collectors normally provide adequate frothing during re~float cleaning steps. In ~ome cases it may be necessary to add a small amount of :Euel oil or a conventional frothing agent, such as the higher alcohols (e.g., methyl isobutyl carbinol), pine oil, cresylic acid, and the like. The amount of frothing agent used depends primarily upon the number of cleaning steps involved, with lar~er amounts being used as the number of cleanin~ steps i8 increased. ~hen used, the ~rothing agent can be incorp-orated into the pulp before, after, or together with the collector and, generally, in a~ounts up to about 0.5 pounds per ton of ore. If the frothing agent is added separately, the pulp is agitated for a sufficient time to insure uniform dispersion of the frothing agënt throughout the pulp.
~ 2~ ~
Generally, an a~,itation time of up to 2 minutes will be sufficient for this purpose.
While t~e solids content of the pulp for flota-tion can vary over a wide range, i~ preferably is within the range of abou~ 5 to about 35 %. Depending on the solids content of the pulp during conditioning, it may be necessary to dilute the pulp with water to obtain the desired value for flotation.
While various conventional cleaning circuits can be used after rougher flotation, in the specific process illustrated in the flow diagram, six re flotation cleaners 20 and a scavenger 22 are used. The tailings 24 and 26 from the first and second cleaners are combined with the rougher tailing 28 and the combined tailings are passedto the scavenger 22 to produce a final tailing 32 which is transferred to a waste pond and a froth 34 which is recycled to ~he rougher 18.
The tailings 35, 36, 38 and 40 from the third, fourth, fifth and sixth cleaners are recycled to the first, second, third and fourth cleaners, respectively.
The process is generally effective for beneficiat-ing siliceous oxidized iron ore; particularly those for which conventional magnetic separation is no~ e~fective. For example, the process can be used ~or beneficia~ing iron ores o~ the type containing hematite, martite, limonite, goethite and mixtures thereof, usually referred to as oxidized ores.
The process also can be used ~or beneficiating magnetic ores, such as magnetite; however, flotation processes usually are not used for magnetic ores because magne~ic separations pro-cesses usually are less expensive. The process generally can be operated at atmospheric pressures and tempèratures, thereby -~ wlS-
6~7 ~
minimizin~ the necessity for special operatin~ conditions or special equipment.
Among the several particular advantages of the process of the invention, probably the most important is the fact a high reco~ery of iron values can be obtained from low-grade ores even ~hough rela~ively small amounts of inexpensive reagents can be employed. Accordingly, the process offers the potential for developing and utilizing huge low-grade iron ore resources which heretofore have not been tapped because ofthe lack of an economical method for beneficiation.
~hile the invention has been described in connec-tion with a system which does not include a desliming step, it should be understood that the conditioning reagent can be used in a system which employs desliming to improve the recovery of iron values.
The ollowing specific examples are presented to illustrate the invention and are not to be construed as limitations thereof.
Example 1 A conditioning reagent in accordance with the invention was prepared by slowly adding, with stirring, 1.5 ml of a 2 % solution of erric nitrate, Fe(N03)3-9 H2O,to 3 ml of a S % solution of "0" Brand sodium silicate solution described above and then stirring ~he resultan~ reaction medium for 1 minute to form a turbid colloidal dispersion. 0.25 ml of 15 % sulfuric acid was then slowly added with stirring to the dispersion at 25 C to form a clear solution. The pH of the resultant solution was 2.4 and the weight ra~ios of the "O"
Brand sodium silicate solution (as purehased~ to the ferric ~ 7 ~72 nitrate an~ to suluric acid werc 5~
600 g of -10 mesh low grade iron ore containing primarily hematite, marti~e and goethite, were ~et ground for S0 minutes in a stainless steel rod mill with an amount of so~a ash equivalent to 2.5 lb./ton of ore and with a suf-ficient amount of deionized wa~er to produce a slurry con-taining about 60 % solids.
The ground charge, abou~ 85 ~/~ of which passed a 500 mesh screen, was transferred to a container and diluted with sufficient additional water to give a pulp containing about 25 weight ~/~ solids. 4.75 ml of thepreviously prepared conditioning reagent (equivalent ~o 0.15 lb. silica/ton of ore, 0.1 lb. ferric nitrate/ton of ore, and 0.1 lb. sulfuric acid/ton of ore) was added to the pulp and the pulp was sub-sequently conditioned for 2 minutes in a laboratory Fagergren machine operated at 1250 RPM, during which time the pH of the pulp was adjusted to about 8.8 by adding sulfuric acid. An amount of PAMAK-4 equivalent to 1.5 lb./ton of ore was then added and the pulp, at a solids content of about 23 ~/O~ was condi~ioned for 1 more minute. An amount of ~o. 2 uel oil equivalent to 0.1 lb./ton of ore was then added and the pulp was conditioned for another 7 minutes.
The conditioned pulp was transferred to a laboratory Fagergren flotation machine, followed by rougher flotation for 6 minutes at 1250 RPM. The rougher concentrate (froth produet) was cleaned by successively re-floating 6 times in flotation cells using fresh water for dilution and without additional conditioning or frothing agents. The final concentrate and tailings were weighed and analyzed for iron. The metallurgical results from this test are summari7.ed in Table I.
~7~Z72 Table I
Product Weight ! % Fe U/o Fe Distri.bution Head 100.0 34~8 100.0 Concentrate 46.9 65.4 88.2 S Tailings 53.1 7.7 11.8 Tests were run in a pilot plant having a continuous circuit similar LO that illustrated in the flow diagram and designed to process 650 pounds o~ ore per hour. The same chemical reagents at approxima~ely the same concentration described above were added to the pulp stream prior to being pumped into conditioners wherein agitation was provided by propeller-type impellers. Several runs were made with the same ore described above and more than about 80 % of the iron was recovered as high grade concentrates in all but a few isolated cases.
Example 2 A variety of non-magnetic iron ores were processed in substantially the same manner described in Example 1, ~ using the same chemical reagents at approximately the same concentration. The same ores were processed with the only commercial flotation process presently being used to any extent which proeess employs a selective floccula~ion deslim ing treatment and a cationic-amine coLlector to float silica rom iron oxide. These ores differed somewhat in chemical and mineralogical characteristics but all included quartz interlocked with the major minerals. The results from these tests are summarized in Table II belo~ wherein the different ores are identiied by the major iron minerals and, under the "Process Used"~heading, "A" designates the process of the invention and "B" designates the commercial process.
~18-~ 7 2 From these results, it can be seen that for the same ores the process of the invention is capable of attain-ing iron recovery significantly higher than that attainable with the commercial process, i.e., about 6 to about 17 % more iron recovery depending upon the particular ore. Similar comparative results have been obtained on specular hematite ores which require a relatively coarse grind for liberation.
From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention, and withou~ departing from the spirit and scope thereof, can make various modifications and changes to adapt the invention to various usages and conditions.
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minimizin~ the necessity for special operatin~ conditions or special equipment.
Among the several particular advantages of the process of the invention, probably the most important is the fact a high reco~ery of iron values can be obtained from low-grade ores even ~hough rela~ively small amounts of inexpensive reagents can be employed. Accordingly, the process offers the potential for developing and utilizing huge low-grade iron ore resources which heretofore have not been tapped because ofthe lack of an economical method for beneficiation.
~hile the invention has been described in connec-tion with a system which does not include a desliming step, it should be understood that the conditioning reagent can be used in a system which employs desliming to improve the recovery of iron values.
The ollowing specific examples are presented to illustrate the invention and are not to be construed as limitations thereof.
Example 1 A conditioning reagent in accordance with the invention was prepared by slowly adding, with stirring, 1.5 ml of a 2 % solution of erric nitrate, Fe(N03)3-9 H2O,to 3 ml of a S % solution of "0" Brand sodium silicate solution described above and then stirring ~he resultan~ reaction medium for 1 minute to form a turbid colloidal dispersion. 0.25 ml of 15 % sulfuric acid was then slowly added with stirring to the dispersion at 25 C to form a clear solution. The pH of the resultant solution was 2.4 and the weight ra~ios of the "O"
Brand sodium silicate solution (as purehased~ to the ferric ~ 7 ~72 nitrate an~ to suluric acid werc 5~
600 g of -10 mesh low grade iron ore containing primarily hematite, marti~e and goethite, were ~et ground for S0 minutes in a stainless steel rod mill with an amount of so~a ash equivalent to 2.5 lb./ton of ore and with a suf-ficient amount of deionized wa~er to produce a slurry con-taining about 60 % solids.
The ground charge, abou~ 85 ~/~ of which passed a 500 mesh screen, was transferred to a container and diluted with sufficient additional water to give a pulp containing about 25 weight ~/~ solids. 4.75 ml of thepreviously prepared conditioning reagent (equivalent ~o 0.15 lb. silica/ton of ore, 0.1 lb. ferric nitrate/ton of ore, and 0.1 lb. sulfuric acid/ton of ore) was added to the pulp and the pulp was sub-sequently conditioned for 2 minutes in a laboratory Fagergren machine operated at 1250 RPM, during which time the pH of the pulp was adjusted to about 8.8 by adding sulfuric acid. An amount of PAMAK-4 equivalent to 1.5 lb./ton of ore was then added and the pulp, at a solids content of about 23 ~/O~ was condi~ioned for 1 more minute. An amount of ~o. 2 uel oil equivalent to 0.1 lb./ton of ore was then added and the pulp was conditioned for another 7 minutes.
The conditioned pulp was transferred to a laboratory Fagergren flotation machine, followed by rougher flotation for 6 minutes at 1250 RPM. The rougher concentrate (froth produet) was cleaned by successively re-floating 6 times in flotation cells using fresh water for dilution and without additional conditioning or frothing agents. The final concentrate and tailings were weighed and analyzed for iron. The metallurgical results from this test are summari7.ed in Table I.
~7~Z72 Table I
Product Weight ! % Fe U/o Fe Distri.bution Head 100.0 34~8 100.0 Concentrate 46.9 65.4 88.2 S Tailings 53.1 7.7 11.8 Tests were run in a pilot plant having a continuous circuit similar LO that illustrated in the flow diagram and designed to process 650 pounds o~ ore per hour. The same chemical reagents at approxima~ely the same concentration described above were added to the pulp stream prior to being pumped into conditioners wherein agitation was provided by propeller-type impellers. Several runs were made with the same ore described above and more than about 80 % of the iron was recovered as high grade concentrates in all but a few isolated cases.
Example 2 A variety of non-magnetic iron ores were processed in substantially the same manner described in Example 1, ~ using the same chemical reagents at approximately the same concentration. The same ores were processed with the only commercial flotation process presently being used to any extent which proeess employs a selective floccula~ion deslim ing treatment and a cationic-amine coLlector to float silica rom iron oxide. These ores differed somewhat in chemical and mineralogical characteristics but all included quartz interlocked with the major minerals. The results from these tests are summarized in Table II belo~ wherein the different ores are identiied by the major iron minerals and, under the "Process Used"~heading, "A" designates the process of the invention and "B" designates the commercial process.
~18-~ 7 2 From these results, it can be seen that for the same ores the process of the invention is capable of attain-ing iron recovery significantly higher than that attainable with the commercial process, i.e., about 6 to about 17 % more iron recovery depending upon the particular ore. Similar comparative results have been obtained on specular hematite ores which require a relatively coarse grind for liberation.
From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention, and withou~ departing from the spirit and scope thereof, can make various modifications and changes to adapt the invention to various usages and conditions.
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Claims (13)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of beneficiating siliceous oxidized iron ores by froth flotation of iron oxide from silica-containing gangue including the steps of forming an aqueous pulp of the ore having a particle size suitable for froth flotation;
conditioning the pulp by adding thereto a pre-mixed conditioning reagent formed by mixing a water-soluble polyvalent metal salt with an aqueous solution of an alkali metal silicate, in an amount sufficient to provide from about 0.05 to about 4 pounds of alkali metal silicate per ton of ore, calculated as SiO2 equivalent, and to provide from about 0.02 to about 2 pounds of polyvalent metal salt per ton of ore, and by adding thereto an effective amount of an anionic collector selective to flotation of iron oxide; and subjecting the conditioned pulp to a flotation operation whereby a concentrate containing a major portion of the iron oxide and a tailing relatively rich in silica are produced.
conditioning the pulp by adding thereto a pre-mixed conditioning reagent formed by mixing a water-soluble polyvalent metal salt with an aqueous solution of an alkali metal silicate, in an amount sufficient to provide from about 0.05 to about 4 pounds of alkali metal silicate per ton of ore, calculated as SiO2 equivalent, and to provide from about 0.02 to about 2 pounds of polyvalent metal salt per ton of ore, and by adding thereto an effective amount of an anionic collector selective to flotation of iron oxide; and subjecting the conditioned pulp to a flotation operation whereby a concentrate containing a major portion of the iron oxide and a tailing relatively rich in silica are produced.
2. A method according to claim 1 wherein said alkali metal silicate is sodium silicate having an Na2O to SiO2 weight ratio within the range from 1:1 to 1:3.75.
3. A method according to claim 1 wherein said conditioning reagent further includes an inorganic acid in an amount sufficient to provide up to about 2 pounds of the acid per ton of ore.
4. A method according to claim 1 wherein said polyvalent metal salt contains a cation selected from the group consisting of iron (ferric and ferrous), copper (cupric), aluminum, lead, chromium, manganese, cobalt, nickel, zinc, cadmium, magnesium, calcium, barium and mixtures thereof.
5. A method according to claim 2 wherein said sodium silicate has a Na2O to SiO2 weight ratio of about 1:3.22 and said polyvalent metal salt is ferric nitrate.
6. A method according to claim 1 wherein said anionic collector is selected from the group consisting of saturated and unsaturated fatty acids containing about 8 to about 20 carbon atoms, water-soluble soaps derived from said fatty acids and mixtures thereof.
7. A method according to claim 1 including the step of adding up to about 0.5 pounds of a frothing agent per ton of ore to the conditioned pulp prior to the flotation operation.
8. A method according to claim 1 including adding a sufficient amount of a water-soluble alkaline inorganic compound, to the pulp prior to the conditioning step to adjust the pH thereof within the range of about 7 to about 11.
9. A method according to claim 8 wherein said alkaline inorganic compound is selected from the group consisting of sodium hydroxide, sodium carbonate, sodium silicate and mixtures thereof.
10. A method according claim 1 to wherein the pH of the conditioned pulp is within the range of about 6 to about 10 prior to the addition of said collector.
11. A method according to claim 1 wherein the solids content of the pulp is within the range of about 5 to about 30% during said conditioning step.
12. A method according to claim 2 wherein said conditioning reagent further includes an inorganic acid in an amount sufficient to provide up to about 2 pounds of the acid per ton of ore;
said polyvalent metal salt contains a cation selected from the group consisting of iron (ferric and ferrous), copper (cupric), aluminum, lead, chromium, manganese, cobalt, nickel, zinc, cadmium, magnesium, calcium, barium and mixtures thereof; and said anionic collector is selected from the group consisting of saturated and unsaturated fatty acids con-taining about 8 to about 20 carbon atoms, water-soluble soaps derived from said fatty acids and mixtures thereof.
said polyvalent metal salt contains a cation selected from the group consisting of iron (ferric and ferrous), copper (cupric), aluminum, lead, chromium, manganese, cobalt, nickel, zinc, cadmium, magnesium, calcium, barium and mixtures thereof; and said anionic collector is selected from the group consisting of saturated and unsaturated fatty acids con-taining about 8 to about 20 carbon atoms, water-soluble soaps derived from said fatty acids and mixtures thereof.
13. A method according to claim 1 wherein the ore in the pulp is a slimy ore.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/759,094 US4132635A (en) | 1977-01-13 | 1977-01-13 | Beneficiation of iron ores by froth flotation |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1076272A true CA1076272A (en) | 1980-04-22 |
Family
ID=25054391
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA284,450A Expired CA1076272A (en) | 1977-01-13 | 1977-08-10 | Beneficiation of iron ores by froth flotation |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US4132635A (en) |
| AU (1) | AU508657B2 (en) |
| BR (1) | BR7800126A (en) |
| CA (1) | CA1076272A (en) |
Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4592834A (en) * | 1983-06-16 | 1986-06-03 | Board Of Control Of Michigan Technological University | Column froth flotation |
| DE3543858A1 (en) * | 1985-12-12 | 1987-06-19 | Didier Werke Ag | METHOD FOR PRODUCING A CATALYST FOR REDUCING NITROGEN OXIDE |
| US4735783A (en) * | 1987-04-22 | 1988-04-05 | Falconbridge Limited | Process for increasing the selectivity of mineral flotation |
| YU11692A (en) * | 1991-02-06 | 1994-06-24 | Denehurst Limited A.C.N. | PROCEDURE FOR TREATMENT OF MATERIAL CONTAINING BASE METAL |
| RU2443474C1 (en) * | 2010-09-27 | 2012-02-27 | Открытое акционерное общество "Михайловский ГОК" | Method of increasing iron-ore concentrate production efficiency |
| RU2537684C1 (en) * | 2013-09-13 | 2015-01-10 | ООО "НВП Центр-ЭСТАгео" | Finishing of rough high-sulphur magnetite concentrate |
| US20160160317A1 (en) * | 2014-12-06 | 2016-06-09 | Sesa Sterlite Limited | Method and system for removing silica from an ore |
| RU2599068C1 (en) * | 2015-06-05 | 2016-10-10 | Общество с ограниченной ответственностью "ЛЕКС ЭЛЕКТА" | Method of processing phosphorous magnetite ore |
| MX2018005586A (en) * | 2015-11-03 | 2018-11-09 | Magglobal Llc | Methods, devices, systems and processes for upgrading iron oxide concentrates using reverse flotation of silica at a natural ph. |
| WO2019068160A1 (en) * | 2017-10-06 | 2019-04-11 | Vale S.A. | Method for concentrating iron ore slurry |
| CN109879293A (en) * | 2019-03-26 | 2019-06-14 | 昆明理工大学 | A kind of method of microfine high-silicon iron ore desiliconization coproduction potassium silicate |
| CN112892854B (en) * | 2020-12-24 | 2022-05-24 | 攀钢集团矿业有限公司 | Method for recycling ilmenite from tailings containing olivine or pyroxene vanadium titano-magnetite iron dressing |
| CN114315099B (en) * | 2021-12-31 | 2024-03-19 | 漳州市龙华矿产有限公司 | Quartz sand prepared from kaolin tailings and preparation method thereof |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1951326A (en) * | 1930-03-31 | 1934-03-13 | Reclamation Company | Process for recovering manganese from ore |
| US2709541A (en) * | 1952-10-16 | 1955-05-31 | Mettler | Measuring spoon with electric vibrating means |
| US2861687A (en) * | 1955-09-09 | 1958-11-25 | Southwestern Eng Co | Flotation of heavy metal oxides |
| US3337048A (en) * | 1964-12-02 | 1967-08-22 | Minerals & Chem Philipp Corp | Method for beneficiating clay by flotation |
| US3589622A (en) * | 1967-04-24 | 1971-06-29 | David Weston | Flotation of metallic oxides iii |
-
1977
- 1977-01-13 US US05/759,094 patent/US4132635A/en not_active Expired - Lifetime
- 1977-08-10 CA CA284,450A patent/CA1076272A/en not_active Expired
- 1977-10-13 AU AU29656/77A patent/AU508657B2/en not_active Expired
-
1978
- 1978-01-10 BR BR7800126A patent/BR7800126A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| AU2965677A (en) | 1979-04-26 |
| BR7800126A (en) | 1978-10-03 |
| AU508657B2 (en) | 1980-03-27 |
| US4132635A (en) | 1979-01-02 |
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| MKEX | Expiry |